Mixing 16 bit linear PCM streams and avoiding clipping/overflow

Question

I\'ve trying to mix together 2 16bit linear PCM audio streams and I can\'t seem to overcome the noise issues. I think they are coming from overflow when mixing samples together.

Answer 1

There's a discussion here: https://dsp.stackexchange.com/questions/3581/algorithms-to-mix-audio-signals-without-clipping about why the A+B - A*B solution is not ideal. Hidden down in one of the comments on this discussion is the suggestion to sum the values and divide by the square root of the number of signals. And an additional check for clipping couldn't hurt. This seems like a reasonable (simple and fast) middle ground.